import java.util.LinkedList;
import java.util.Queue;

public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        //遍历创建
        TreeNode A = new TreeNode('a');
        TreeNode B = new TreeNode('b');
        TreeNode C = new TreeNode('c');
        TreeNode D = new TreeNode('d');
        TreeNode E = new TreeNode('e');
        TreeNode F = new TreeNode('f');
        TreeNode G = new TreeNode('g');
        TreeNode H = new TreeNode('h');
//        TreeNode I = new TreeNode('i');
//        TreeNode J = new TreeNode('J');
//        TreeNode K = new TreeNode('K');
        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        E.right = H;
//        D.left = I;
//        D.right = J;
//        E.left = K;
        return A;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if (root == null) {
            return ;
        }
        System.out.print(root.val + "  ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if (root == null) {
            return ;
        }
        inOrder(root.left);
        System.out.print(root.val + "  ");
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if (root == null) {
            return ;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val + " " );
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
        if (root == null) {
            return ;
        }
        nodeSize++;
        size(root.left);
        size(root.right);
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int left = size2(root.left);
        int right = size2(root.right);
        return 1 + left + right;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if (root == null) {
            return;
        }
        if (root.left == null && root.right == null) {
            leafSize++;
            return;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        if (root.left == null && root.right== null) {
            return 1;
        }
        int left = getLeafNodeCount2(root.left);
        int right = getLeafNodeCount2(root.right);

        return left + right;
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if (root == null) {
            return 0;
        }
        if (k == 1 && root != null) {
            return 1;
        }
        int left = getKLevelNodeCount(root.left , k -1);
        int right = getKLevelNodeCount(root.right , k -1);

        return left + right;
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int left = getHeight(root.left);
        int right = getHeight(root.right);
        return left > right ? left + 1 : right + 1;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if (root == null) {
            return null;
        }
        if (root.val == val) {
            return root;
        }
        TreeNode left = find(root.left,val);
        if (left != null) {
            return left;
        }
        TreeNode right = find(root.right,val);
        if (right != null) {
            return right;
        }
        return null;
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        TreeNode cur = null;
        while (!queue.isEmpty()) {
            cur = queue.poll();
            System.out.print(cur.val + " " );
            if (cur.left != null) {
                queue.offer(cur.left);
            }
            if (cur.right != null) {
                queue.offer(cur.right);
            }
        }
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if (root == null) {
            return true;
        }
        if (root.right != null && root.left == null) {
            return false;
        }
        if (root.left == null && root.right == null) {
            return true;
        }
        boolean left = isCompleteTree(root.left);
        boolean right = isCompleteTree(root.right);
        return left && right;
    }
}
